It is known in the art to input data to various forms of data processing devices by the use of keyboards having a plurality of input keys, wherein each key corresponds to a particular data element such as an alphanumeric character. A typical configuration of such a keyboard is known as a "QWERTY" configuration, wherein the first six switches on one of the keyboard rows respectively represent the alphabetic characters Q, W, E, R, T and Y. However, such keyboards require a large number of keys and switches, and thus require a large amount of space, mitigating against true portability.
It is also known in the art to use a single configuration of a small number of switches for inputting a character to a data processing device by operating particular subgroups of the switches to represent particular characters, as illustrated by Curtin et al. U.S. Pat. No. 4,727,357, commonly assigned herewith. The disclosure of U.S. Pat. No. 4,727,357 is incorporated herein by reference. In the input configuration disclosed therein, switches are arranged in a particular mosaic layout, as segments of a standard "figure 8" or "British flag" configuration. Switches corresponding to segments of the mosaic which together form a shape of a particular character are operated to input that character to a data processing device.
As disclosed in the prior U.S. Pat. No. 4,727,357 patent, each switch is associated with a display bar representing a segment of the "figure 8" or other mosaic configuration, so that the mosaic segments activated by the user are displayed while a character is being entered. It should be appreciated that such display bars may be light emitting, light transmitting, or any other type which provides different optical characteristics in response to activation or deactivation, or in response to presence or absence of a selecting control signal or the like.
After each switch operation and based on the inputted segments of the mosaic display, the data processing device may "guess" at the character being inputted by the operator, and display a list of characters which may correspond to the particular pattern of switches thus far operated. The disclosed system thus enables the operator to shorten the data input process by selecting the input character from the characters displayed in the list. However, in the device of the U.S. Pat. No. 4,727,357, characters having a large number of segments (such as the letter "M") require a longer sequence of input switch activations than that required for characters having a smaller number of segments (such as the letter "I").
Thus, for a known segment input device which is usable instead of a keyboard the input procedure tends to be lengthy and time consuming, when compared with a character input procedure using one-switch per character, as available in a standard keyboard.
In view of the large variation in the number of segments in the inputted characters, wherein an "I" has only two input segments for example while an "M" has 6 input segments, it is thus difficult to use the concepts of the above described prior art to input character data with a fixed, predetermined, number of switch activations for each character.
Thus, data input with the prior art device requires a variable number of switch activations and fails to provide an efficient method and apparatus for input of character data which is competitive with a standard keyboard in data input speed. For that reason, known PDA devices, such as the "Newton" available from Apple Computer Inc., Cupertino, Calif., include data input arrangements utilizing a handwriting recognition process, for recognizing a handwritten input message. Such messages are inputted to the known PDA by an operator with the aid of a stylus, or pen component, of the PDA acting in conjunction with a pen sensing display for example. As an alternative data input arrangement, such a PDA also utilizes a simulated keyboard wherein a miniaturized keyboard is displayed on the pen sensing display, and the operator selects specific characters by selecting a particular simulated key with the aid of the input stylus.
However, known handwriting recognition techniques are slow and, unless significantly more storage is provided than is feasible for such portable PDA devices, are subject to errors. Moreover, since the object of PDA devices is to provide a small, compact, data manipulation device, the displays available with such devices are necessarily small. Accordingly, the simulated keyboard keys displayed by a PDA are small and require precise pointing with the stylus thereof. Such a requirement for precise pen positioning with respect to a small image of a keyboard key thus further slows the process of inputting data to the PDA.
There is thus a need in the prior art for a compact data input device which operates efficiently, quickly and reliably for inputting character data to data processing devices.
There is a more specific need in the art for a reliable compact data input device which permits input of character data to a data processing device using a fixed number of operations for each of the input characters.
There is yet a further need in the prior art for a compact data input device wherein an operator is permitted a degree of imprecision, so that a sequence of operator input operations which do not match, but are sufficiently close to, a required sequence for inputting a particular character is nonetheless recognized as the required input sequence for the particular character.